If your driving it from pronterface rather than running the print off the SDCard, it's most likely to be a problem with the USB connection.
I'd try reducing the comms frequency, and a different USB cable, one with ferite cores on either end.
I don't use pronterface, if it has a setting for verbose output, you should see what errors/warnings Marlin is throwing when it gets into the state.
I run Marlin with SDCard support and LCDSupport, on both my printers and one of my 2 printers has neither, but disabling it is just a question of commenting out the line in configuration.h.
